Question 1

Which of the following best describes the primary function of the nuclear envelope in a eukaryotic cell?

Accepted Answer

It regulates the passage of molecules between the nucleus and cytoplasm through nuclear pores.

Question 2

During which phase of the cell cycle are chromosomes most visible and distinct under a microscope, and why is this important for clinical cytogenetic analysis?

Accepted Answer

Metaphase, because chromosomes are highly condensed and aligned.

Question 3

A cytogeneticist identifies a chromosomal abnormality at 7q31.2. According to standard nomenclature, where is this location found?

Accepted Answer

Chromosome 7, long arm, region 31.2

Question 4

Which of the following statements about the structure of DNA is correct?

Accepted Answer

Guanine pairs with cytosine via three hydrogen bonds.

Question 5

If a DNA molecule contains 30% adenine, what percentage of guanine would you expect to find?

Accepted Answer

$$20\%$$

Question 6

Which of the following best explains why G-C rich regions of DNA are more stable than A-T rich regions?

Accepted Answer

G-C pairs form three hydrogen bonds, while A-T pairs form two.

Question 7

Which of the following is a correct description of euchromatin?

Accepted Answer

It is less densely packed and more transcriptionally active.

Question 8

A researcher is studying a region of DNA that is tightly wound around histone octamers and is not accessible to transcription machinery. Which type of chromatin is this most likely to be?

Accepted Answer

Heterochromatin

Question 9

Which of the following best describes the role of nucleosomes in the organization of nuclear DNA?

Accepted Answer

They compact DNA by wrapping it around histone proteins.

Question 10

A geneticist is mapping the distance between two loci using recombination frequency. Which unit is traditionally used for this measurement?

Accepted Answer

CentiMorgan (cM)

Question 11

Which of the following is true regarding the orientation of DNA strands in the double helix?

Accepted Answer

The strands are antiparallel, one running 5’ to 3’ and the other 3’ to 5’.

Question 12

Which of the following best describes the difference between constitutive and facultative heterochromatin?

Accepted Answer

Constitutive heterochromatin consists of repeat DNA and is always inactive, while facultative heterochromatin can be regulated to become active.

Question 13

A patient’s karyotype reveals 47 chromosomes, including an extra chromosome 21. Which of the following best describes this condition?

Accepted Answer

Down syndrome

Question 14

Which of the following is a correct statement about the Y chromosome?

Accepted Answer

It is a small chromosome containing male sex-determining genes.

Question 15

Which of the following best explains why the Giemsa stain is useful in cytogenetics?

Accepted Answer

It produces characteristic banding patterns that help identify chromosomal regions.

Question 16

Which of the following is a real-world application of understanding chromatin structure and histone modification?

Accepted Answer

Developing cancer therapies that reactivate silenced tumor suppressor genes.

Question 17

A DNA sample is heated to separate its strands and then cooled to allow them to re-anneal. Which property of DNA allows this process to occur?

Accepted Answer

The complementary base pairing between nucleotides.

Question 18

Which of the following best describes the function of telomeres?

Accepted Answer

They protect chromosome ends from degradation during cell division.

Question 19

Which of the following is a correct pairing of purines and pyrimidines in DNA?

Accepted Answer

Guanine (purine) pairs with cytosine (pyrimidine)

Chromosome and DNA Structure: Organization, Visualization, and Compaction in Eukaryotic Cells

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